Researchers to develop methods for discovering new metallic glasses

Bulk metallic glasses, or BMGs, are a new class of metal alloys with a variety of attractive properties. However, applications have lagged because scientists cannot predict which combinations of elements can be cooled from the liquid to yield a glassy atomic alloy structure in large sizes. With a $1.55 million grant from the National Science Foundation, several UW-Madison materials researchers will tightly integrate computation and experiments to develop new methods for accelerated discovery of new metallic glasses with desired properties.

A BMG can be cooled from the liquid without crystallization, resulting in a glassy, amorphous solid. Now, after more than 20 of alloy development, real applications in areas that include packaging, arterial stents, water purification, and miniature gears and springs finally are on the horizon, in part because because researchers have generated enough known BMGs with a wide spectrum of properties. For example, various BMGs have a variety of attractive properties, including high elastic modulus, yield strength, specific strength, and good biocompatibility.

Researchers can process sufficiently stable BMGs like plastics if they hold the temperature in the supercooled liquid region, resulting in net-shape, seamless forming of complicated shapes by blow molding and rapid fabrication of nanostructures across large areas by hard-mask imprinting. However, with the current state of the art in materials design for BMGs, researchers cannot predict whether a given alloy composition will form a glass. Various empirical, thermodynamic and structural guidelines have been proposed, but none of them reliably predict new glasses.

Predicting glass formation is difficult because it is governed by a complicated interplay between nucleation of the crystal phase(s) and atom dynamics in the supercooled liquid, both of which involve atomic structure that is hard to measure and timescales that are hard to simulate.

In its research, the UW-Madison team will develop new methods for discovering new BMG alloys using an iterative strategy of state-of-the-art experimental and computational tools that advances the objectives of the U.S. Materials Genome Initiative (MGI). Tapping complimentary expertise, the researchers will provide new insight into the contributions to stabilizing BMGs from atom dynamics, transport and crystal nucleation from cluster dynamic simulations starting from experimentally determined refined structures and transformation kinetics. For example, the researchers will apply the new methodology to develop new, bulkier aluminum-based metallic glasses, starting from the aluminum-samarium and aluminum-lathanum systems, stabilized by minor alloying. In the process of developing and applying the methodology, the researchers expect the project will support discovery of new underlying connections between structure and glass formation in metals from the atomic to nanometer scale.

The novel integrated computational and experimental approach, combining structure up to the nanometer scale and the kinetics of both glass formation and crystallization, may be transformative in yielding a unique combination of tools and approaches that may lead to a general method to design new BMGs alloys for a variety of applications.

This project will support the education of students and postdoctoral students in combined experimental and computational materials research in a collaborative environment, and development of outreach materials and demonstrations for younger students and the public through various UW-Madison programs.